Synergistic effect of doripenem in combination with cefoxitin and tetracycline in inhibiting NDM-1 producing bacteria

Aim: To propose newer combinations of antibiotics effective against NDM-1-producing bacterial strains. Materials & methods: Antibiotics combinations were tested by checkerboard assay. NDM-1 protein/enzyme was expressed and purified to perform enzyme kinetics, circular dichroism and fluorescence spectroscopic studies. Results: Doripenem–cefoxitin combination and doripenem–tetracycline combination showed synergistic effect toward NDM-1-producing strains. The catalytic efficiency of NDM-1 enzyme was decreased drastically by 96.6% upon doripenem–cefoxitin treatment and by 35.54% after doripenem–tetracycline treatment. Conformational changes were observed in NDM-1 upon combination treatment. Conclusion: NDM-1-producing bacterial strains show resistance to multiple antibiotics but the combination of doripenem–cefoxitin and doripenem–tetracycline are effective against them. The combination of a carbapenem and cephamycin antibiotic is proposed for future treatment options against bacteria-producing NDM-1.